UU groups can have "pulpit supply", where a different minister comes every week simply to preach, and doesn't get involved in the church politics at all. Others (including mine) have part-time ministry, where the minister is under contract, preaches 1 or 2 times per month, attending some meetings, and giving pastoral care. The other Sundays in the month are handled by supply ministers, or by the laity.
However, there aren't many ministers who are willing to be involved as a consultant on a short-term basis of less than a year. They have to make a living as well, and it's hard to get involved at a deep level unless you're willing to move to the town the church is in. Members of the UU Ministers' Association have a considerable investment in training and internship, and good ones look for a group who's willing to work with them long enough for the relationship to be productive.